Physiology Feeding and Satiety Flashcards
What is energy homeostasis?
Physiological process whereby energy intake is matched to energy expenditure over time
How do you calculate BMI?
Weight/Height(m) (squared)
What BMI is thin or normal?
Up to 25
What is classed as overweight?
25-29.9
What is classed as obese?
30-39.9
What is classed as morbidly obese?
BMI of more than 40
What are the major factors influencing obesity?
Genetics - fatness runs in families
Environment - westernisation of diet
What is energy balance disturbance?
Difference between energy intake and expenditure
What can obesity lead to, in terms of contribution to disease and premature mortality?
Type 2 diabetes High BP Heart attack Cancers (colon) Osteoarthritis
Why do we need fat?
Energy storage
Prevention of starvation
Energy buffer during prolonged illness
Why can it be difficult to lose weight in terms of the brain?
Increased body fat alters the brain function, long term obesity induces brain ‘re-programming’.
Your brain views the extra weight/fat as normal and dieting as a threat to body survival (i.e. it defends the new weight)
How does the CNS influence energy balance and body weight?
Behaviour - feeds and physical activity
ANS activity - regulates energy expenditure
Neuroendocrine system - secretion of hormones
What might damage of the ventromedial hypothalamus cause?
Obesity
What might damage of the lateral hypothalamus cause?
Leanness
What is satiation?
The sensation of feeling full during a meal
What is satiety?
The period of time between meals
What is adiposity?
The state of being obese
Do satiation signals increase during meals to limit meal size?
YES
Describe the 5 secretions that are secreted - satiation signals?
Cholecystokinin (CCK) Peptide YY (PYY3-36) Glucagon-like peptide 1 (GLP-1) Oxyntomodulin (OXM) Obestatin
Describe what CCK - cholecystokinin does?
It is secreted from the enteroendocrine cells in the duodenum and jejunum.
It is release in proportion to lipids and proteins in meals.
It signals via sensory nerves to hindbrain and stimulates hindbrain directly (Nucleus of solitary tract (NTS))
Describe what PYY3-36 - peptide YY does?
It is secreted from endocrine mucosal L-cells of the GI tract
Levels increase rapidly post meal.
It inhibits gastric motility, slows emptying and reduces food intake (hypo)
What does GLP-1 - glucagon like peptide 1 do?
It is a product of pro-glucagon gene.
It is also released from L cells in response to food ingestion.
It inhibits gastric emptying and reduces food intake (Hypo, NTS)
Describe what OXM - oxyntomodulin does?
It is also a produce of pro-glucagon gene and it is released from oxyntic cells of the small intestine after a meal.
It surpasses the appetite
What is obestatin and what does it do?
It is a peptide produces from the gene that encodes ghrelin and it is released from cells lining the stomach and small intestine.
What is ghrelin?
It is a hunger signal
What is ghrelin secreted by?
Oxyntic cells in the stomach
What happens to the levels of ghrelin before meals and after meals?
Increase before meals
Decrease after meals
What 2 hormones report fat status to the brain?
adiposity signals
Leptin
Insulin
Describe where leptin is made and released?
From the fat cells
Describe where insulin is made and released from?
The pancreatic cells
How do the levels of leptin and insulin in the blood vary as more fat is stored?
Levels in the blood increase as more fat is stored
What does reduced leptin mimic and thus cause?
Mimics starvation causing unrestrained appetite
What are some of the biological roles of leptin?
Food intake/energy expenditure/fat deposition
Peripheral glucose homeostasis/insulin sensitivity
Maintenance of immune system
Maintenance of reproductive system
Angiogenesis
Tumourigenesis
Bone formation
What is the current treatment for obesity?
Orlistat
What does orlistat do?
Inhibits pancreatic lipase, decreasing triglyceride abdorption
Reduced efficiency of fat absorption in small intestine
What are some side effects of orlistat?
Side-effects include cramping and severe diarrhoea
Describe gastric by pass surgery
Produces substantial weight loss in one year thats sustainable
Surgery induces high level of completely resolution of type 2 diabetes
What is Adaptive Thermogenesis?
This can be defined as the regulated production of heat in response to environmental changes in temperature and diet, resulting in metabolic inefficiency. For example, shivering when we are cold uses energy and this is an example of adaptive thermogenesis
